I have both and if you asked me a month ago I would have said the .25 cal hands down, however I converted my .30 cal Impact to a .22 and used a 700 Superior liner and all I can saw is WOW !!! I am shooting the new JSB 25.4 gr KO slugs and am totally blown away with the accuracy out past 200 yards. At 50 yards its ridiculous, pretty much in same hole, at 100 yards I am printing 1/2" groups and today I was shooting a Bush's baked bean can at 175 yards and hitting every time. My regulator is set @ 140 BAR and velocity is just under 1000 FPS. One advantage the .25 has is shot count and efficiency, my regulator is set @ 100 BAR and am shooting 25.4 JSB's around 930 FPS with a huge shot count from a 250 BAR fill, the .25 Impact is pretty accurate out to say 150 yards but the wind pushes pellets around much more than the .22 KO slugs.